The effects of changes of heading on some steering compasses are well known and are tabulated as deviation. Heeling can also displace a compass needle in some vessels on certain headings, especially those with a large chunk of iron ballast. For practical purposes it is all but impossible to tabulate ‘heeling error’, but this will not make it go away. The answer when you are sailing a long leg at a steep angle of heel is to check your heading against the handbearing compass held in a position you know to be magnetically inactive.