UK

Paid maternity leave is 39 weeks (37 is shareable). Total protected leave is 52 weeks (50 of which is shareable). Since pay is at 90% for the first 6 weeks, we attribute 6 weeks to maternity leave and 33 to paid and 44 to protected shareable leave weeks. Source First 6 weeks are paid at the rate of 90% of average gross weekly earnings with no cap. The rest of the paid leave ia a maximum of £187.18/week for 33 weeks (however this is counted in shareable). Source

37 paid shareable weeks and 50 protected shareable weeks that reduce maternity to increase paternity. Since maternity pay is 90% of salary for 6 weeks, to maximise financial support 6 is attributed to the birth parent. Source We assumed birth parent takes 6 weeks as it's at a higher rate and 33 weeks of paid leave is the shareable, which is maximum £187.18/week. Source

Up to 2 weeks. Source Max £187.18/week for up two weeks. Source

18 weeks of unpaid parental leave is available for both parents for each child up to the point the child turns 18 years old. Only 4 weeks can be taken per year and leave has to be taken as whole weeks. Source No pay for parental leave from government. Source

Assuming birth parent takes all shareable leave, they have 39 weeks of taxed (income and national insurance) paid leave, 6 of which is comensated at 90% and the remaining 33 topping out at £187.18/week. To work out net maternity pay we need to subract income tax and national insurance. National insurance is calculated per pay period, so while there's no national insurance in the 33 weeks £187.18 income, there will be for the 6 weeks of 90%. Income tax is paid yearly with a personal allowence of £12,570, so we need to work out total income for the year and attribute tax paid per week to maternity pay. Birth parent is entitled to a total of 52 weeks of protected leave, which if they take, while their income for the year goes down (they wouldn't have the additional 13 weeks salary) the net support from the government goes up, as they pay less tax on the government support they receive.

Assuming the non-birth parent takes none of the shareable leave in, they are entitled to 2 weeks of £187.18/week. This is below the national insurance threshold of £242, which is collected per pay period. However we need to attribute income tax. As all of the personal allowence (£12,570) is used up for income from work, this effectively means paternity pay is taxed at 20% regardless if the non-birth parent decides to take their 4 weeks of unpaid parental leave also.