This varies a lot depending on Wehrmacht or Red Army, on the type of the tank and who was advancing or retreating.

Armor protection and enemy gun performance:

Different tanks had different tolerance to damage and a tank like Panzer VI Tiger for example was more expensive and thus a more viable candiate for the workshop than a Bt-7 for example. If your tank is better protected to enemy fire you will suffer a higher proportion of mobility losses and mines. These damages are more likely to get repaired.

The Tiger in 1943 ( Kursk for example ) was so well protected that damage done by russian tanks or anti tanks guns was rarely enough to destroy a Tiger. In practical terms pretty much no russian Tanks or a very small number completly destroyed a Tiger during this battle. So a T-34 or a anti tank crew maybe hit a tiger several times and reported it as knocked out when they had to retreat while the tank was just not moving or had some damage to the tracks. A Tiger would mainly sustain damage through mines or terrain. So to give an extreme example, a Tiger counted as destroyed during russian retreat was with near certainty not knocked or let alone destroyed.

On the other hand, cheap tanks like the Bt series for example would likely be destroyed when hit by an upgunnded Panzer IV or a Panther or a Tiger. Counted kills would likely be pretty close to the actual losses.

What will the crew report

My point is, tank crews would report kills for example when they hit the tank and it burned out, which is a good indicator for a really destroyed tank, but they would also maybe report a kill when they hit a tank then have to retreat and just assume it was knocked out. Over long distances its hard to tell if a tank got hit hard, thus the Wehrmacht guideline to hit a tank until it burns out. Its very hard to assess the damage done to a tank over longer distances. Maybe your hit killed the crew and damaged the badly assembled tank that the entire hull deformed and rendered it useless, but it looks like nothing happended. Obviously this leaves the tank with better gun with a naturally higher accuarcy because its hits were more likely to cause damage beyond repair. To stick with with Kursk 43, if a Tiger commander hits a russian tank its very unlikely that the other tanks doesn't sustain heavy damage. This leaves deliberate overclaiming and retreat/advance out of the equation.

Retreat/Advance

When you retreat you are less likely to recover damaged vehicles. The reported kills will be more accurate to the actual loss of the enemy if you advance.

German example

German claims for destroyed tanks were found to be pretty accurate. Historians like Frieser for example conclude with cross checking claims and losses that the claims were quite accurate. To give a bit more substantial argument the inteligence service of the Wehrmacht took take claims and substracted 30% to estimate enemy strenght. This means from the knocked out claims the OKW estimated that 7 out of 10 were complete losses. This doesn't mean that the other 3 were made up, it would happen often that a knocked out tank was recovered and not a total loss. The claim for a knocked out tank was correct but it was no total loss. For the russian side the tank claims seem to be more exccesiv. Does this mean russian tank crews made up kills? No, a german tank on average would inflict significantly higher damage. Russian tank crews had a harder job assesing the damage done on enemy tanks