Of the three ratios, only LTV (loan to value) is binding in October 2026: 80 %, or 90 % under 36; the ČNB (Czech National Bank) deactivated DSTI on 1 July 2023 and DTI on 1 January 2024. In practice a bank may lend you at most that share of its own valuation of the property, and the rest comes from your own funds.
DSTI and DTI are now simply the thresholds banks set for themselves, typically 45 % of net income going on repayments and total debt of 8–9.5 times annual income.
The difference has practical consequences. No bank will take you past the LTV cap, whereas DSTI and DTI thresholds vary between banks, and for a client with a high, stable income a bank can stretch them. Below, each ratio is worked through, and one household's numbers show which of them bites first. The other requirements, such as documents, age or residence, are covered in our first-time buyer guide.
The three ratios in one table
| Ratio | What it measures | How it is calculated | Threshold in October 2026 | Who sets it |
|---|---|---|---|---|
| LTV (loan to value) | the loan against the value of the collateral | loan ÷ collateral value × 100 | 80 %, 90 % under 36 | ČNB, binding |
| DSTI (debt service to income) | how much of your income goes on repayments | repayments on all loans ÷ net monthly income × 100 | usually 45 %, 50 % under 36 (40–50 % depending on the bank) | the bank; the ČNB deactivated its limit on 1 July 2023 |
| DTI (debt to income) | all your debts relative to income | outstanding balances of all loans ÷ net annual income | usually 8–9.5 times | the bank; the ČNB deactivated its limit on 1 January 2024 and advises extra caution above DTI 8 |
| Investment mortgage | a flat to let, a third or further property | LTV and DTI as above | recommended LTV 70 % and DTI 7 | ČNB, recommendation from 1 April 2026 |
The ČNB has had the legal power to cap all three ratios since 2022 (§ 45a–45c of the Czech National Bank Act). It can therefore switch DSTI and DTI back on if it decides households are borrowing too heavily. In October 2026 only LTV is fixed, and even here the law leaves banks a small exception: they may lend above 80 % for no more than 5 % of new lending volume per quarter.
LTV is based on the valuation, not the price
The figure LTV is measured against is not the price you agreed with the seller but the collateral value set by the bank's valuation (odhad). If the valuation lands below the purchase price, the bank lends 80 % of the lower number and you cover the gap from your own funds. What to do when that happens is explained in Property valuation for a mortgage.
The 90 % exception is for applicants under 36 buying a home to live in. One applicant meeting the age condition is enough. It does not apply to a flat bought as an investment. The details, and what the exception really costs, are in Mortgages for under-36s.
LTV also shows up in the price. Many banks keep their lowest advertised rate for loans up to 80 % of the value; Moneta, for example, offered a rate from 4.59 % with a one-year fixation in September 2026 on exactly that condition. If you pledge a second property as well, the bank calculates LTV from the two valuations combined. That is how using the parents' flat or house as additional collateral works.
How is DSTI calculated?
DSTI adds up every monthly repayment: the new mortgage, consumer loans, leasing and a share of the limits on credit cards and overdrafts, including ones you never use. The total is set against the net income you can document. At the usual 45 % threshold, a household with net income of CZK 60,000 may spend at most CZK 27,000 a month on all its loans together. Most banks allow up to 50 % for applicants under 36.
DSTI is not the only income test, though. The bank also checks that the household has enough left to live on once the repayments are paid, and it sets that calculation itself according to the number of adults and children. A family with two children can therefore hit the ceiling before a childless couple with the same DSTI. What the bank deducts from your income and how to lift the ceiling is covered in 12 steps to better creditworthiness.
DTI watches your total debt
DTI divides the outstanding balances of all your loans by annual net income. At DTI 8 and net income of CZK 60,000 a month, which is CZK 720,000 a year, the household may owe at most CZK 5,760,000.
At today's rates DTI rarely stops anyone before DSTI does. Repayments of 45 % of income at 5.00 % over 30 years correspond to a loan of roughly seven times annual net income, which is less than DTI 8 allows. Only at a rate of around 3.8 % would the order reverse. In practice DTI holds back two groups: people who already carry another debt with a large balance and a small repayment, and investment buyers, for whom the ČNB has recommended DTI of no more than 7 since 1 April 2026.
Which limit will stop you?
Whichever of the three gives the smallest loan, so work out all three, as the Nováks did.
The Nováks in numbers (aged 38 and 40, household net income CZK 70,000, a car loan with a CZK 4,000 repayment and CZK 150,000 outstanding, a flat priced at CZK 5,500,000 and valued at CZK 5,300,000; annuity repayments, 5.00 %, 30 years, the bank's internal thresholds of DSTI 45 % and DTI 8):
- LTV: 80 % × CZK 5,300,000 = CZK 4,240,000.
- DSTI: 45 % × CZK 70,000 = CZK 31,500; after the car loan, CZK 27,500 is left for the mortgage. That supports a loan of CZK 5,122,744.
- DTI: 8 × CZK 840,000 = CZK 6,720,000; after the car loan, CZK 6,570,000.
LTV is what stops them. A CZK 4,240,000 mortgage means a repayment of CZK 22,761, DSTI including the car comes to 38.2 % and DTI to 5.2. The Nováks have to find CZK 1,260,000 themselves, plus the costs of buying. Had they been buying a flat for CZK 7,000,000 with a valuation to match, LTV would allow CZK 5,600,000 and DSTI, at CZK 5.12 million, would become the limit.
Now run the same numbers at a higher rate. At 6.00 % the repayment on CZK 4,240,000 over 30 years would be CZK 25,421 and DSTI including the car 42 %. They would still pass, but their margin would shrink to a few thousand crowns. The How much can I borrow calculator works out your own combination of limits.
Using the ratios before you apply
- Base your LTV on a cautious valuation, not the advertised price. Prices of older flats rose 14 % year on year in Q2 2026, and at that pace valuations lag behind prices more often.
- Cancel unused credit cards and overdrafts before you apply. The bank counts them in DSTI even when you owe nothing on them.
- Ask which DSTI and DTI thresholds the bank actually works with. The gap between 40 and 50 % DSTI is worth roughly CZK 1.1 million of loan at net income of CZK 60,000 and a rate of 5.00 % over 30 years.
- Don't treat the bank's ceiling as a target. Work out your repayment at a rate 1 pp higher too, because you will be negotiating the rate again when the fixed period ends.
Sources
- ČNB – Setting upper limits on the LTV, DSTI and DTI credit ratios
- Act No. 6/1993 Coll., on the Czech National Bank, § 45a–45c
- Act No. 257/2016 Coll., on consumer credit, § 86 (creditworthiness assessment)
- ČNB – recommendation of stricter limits for investment mortgages (LTV 70 %, DTI 7)